Multi-Level Modeling of Total Ionizing Dose in a-SiO2: First Principles to Circuits

• Main Author: Nicklaw, Christopher J
• Other Authors: Ronald D. Schrimpf
• Format: Others
• Language: en
• Published: VANDERBILT 2003
• Subjects: Electrical Engineering
• Online Access: http://etd.library.vanderbilt.edu/available/etd-07242003-120620/

Oxygen vacancies have long been known to be the dominant intrinsic defect in amorphous SiO2 . They exist, in concentrations dependent on processing conditions, as neutral defects in thermal oxides without usually causing any significant deleterious effects, with some spatial and energy distribution. During irradiation they can capture holes and become positively charged E´-centers, contributing to device degradation. Over the years, a considerable database has been amassed on the dynamics of E´-centers in bulk SiO2 films, and near the interface under different irradiation and annealing conditions. Theoretical calculations so far have revealed the basic properties of prototype oxygen vacancies, primarily as they behave in either a crystalline quartz environment, or in small clusters that serve as a substitute for a real amorphous structure. To date at least three categories of E´ centers, existing at or above room temperature, have been observed in SiO2 . The unifying feature is an unpaired electron on a threefold coordinated silicon atom, having the form O3 ? Si*. Feigl et al. identified the E´1 center in crystalline a-quartz as a trapped hole on an oxygen vacancy, which causes an asymmetrical relaxation, resulting in a paramagnetic center. The unpaired electron in the E´1 center is localized on the three-fold coordinated Si atoms, while the hole is localized on the other Si atom. Results from an ab initio statistical simulation examination of the behaviors of oxygen vacancies, within amorphous structures, identify a new form of the E´-center, the E´g5, and help in the understanding of the underlying physical mechanisms involved in switched-bias annealing, and electron paramagnetic resonance (EPR) studies. The results also suggest a common border trap, induced by trapped holes in SiO2, is a hole trapped at an O vacancy defect, which can be compensated by an electron, as originally proposed by Lelis and co-workers at Harry Diamond Laboratories. This dissertation provides new insights into the basic mechanisms of a-SiO2 defects, and provides a link between basic mechanisms and Electronic Design Automation (EDA) tools, providing an enhanced design flow for radiation-resistant electronics.